juddering and bad idle?

[Joe_Mk5]

right guys, another little problem with the polo (N)
i had a new clutch put in by my trusted garage a few weeks back, when i put my foot down the car seems to judder and almost slip a gear?
it happens on all gears.
also just as i drove home earlier, i put in £10 worth of fuel drove dow a few roads back to my house, stopped and the car just seemed to judder real bad on idle. i was a little curious to what it could be so took it for a spin and the car constantly felt like it was about to stall. the juddering got worse when i put my foot down again.
any ideas guys?

i really really hope its not the gear box =[

cheers in advance

[Joe_Mk5]

just been doing a bit of research,
could it possibly be a dirty throttle body?
the car has done around 76k
cheers!